Several human conditions are associated with abnormalities in lymphocyte function. Recently circulating suppressor cells have been implicated as etiologic or contributory in the depressed cellular and/or humoral immune responses associated with some disease states. We have described a prostaglandin (PG) producing suppressor cell in human peripheral blood. Increased activity of this cell appears to be responsible for the depressed cellular immunity seen in Hodgkin's Disease and in old age. In the proposed study, I wish to examine the activity of the PG producing suppressor cell in other disease states, and to further characterize this cell in normals and in disease states, with respect to the nature of the cell (T-cell, B-cell, macrophage) and mode of action. I also propose to inhibit this cell in vivo with indomethacin, a PG synthetase inhibitor, in an attempt to restore normal cellular immunity in patients with Hodgkin's Disease, old age, or common variable hypogammaglobulinemia. A third aspect of this study is an investigation of suppressor cells active in humoral immunity in humans. I propose to establish an in vitro assay for human immunoglobulin synthesis and study the effects of prostaglandins, histamine, and other putative mediators of suppression in this system. Compounds that do exert suppression will be further examined by "subtracting" them from the assay by inhibiting their endogenous synthesis or blocking them at the receptor level. In this way, I hope to characterize any suppressor cell in the humoral immune system that acts via any of the compounds tested.